1. Field of the Invention
The present invention relates generally to panelboard assemblies and, more particularly, to a panelboard assembly employing a gas segregator barrier for avoiding inadvertent flow of electrical current due to ionized exhaust gases being discharged from electrical switching apparatus therein. The invention also relates to gas segregator barriers for electrical switching apparatus.
2. Background Information
Panelboard assemblies are power distribution devices used in residential, industrial and commercial applications. Panelboards typically comprise a wall mounted box enclosure supporting conductive bus bars and electrical switching apparatus (e.g., without limitation, circuit switching devices and circuit interrupters such as circuit breakers, contactors, motor starters, motor controllers and other load controllers) electrically connected to the bus bars.
Panelboard assemblies often include pairs of adjacent circuit breakers connected in an end-opposing, “double-branch” arrangement, to bus bars carrying current of the same electrical phase. See, for example, U.S. Pat. Nos. 4,783,718; 4,965,544; and 5,150,091.
Circuit breakers typically have a molded plastic housing enclosing at least one pair of separable contacts. When the separable contacts are opened, under overload, short circuit or fault conditions, an arc is usually created which is accompanied by the generation of ionized gases. Such ionized gases are typically discharged through vents in the molded plastic housing and, when discharged from one of the closely aligned circuit breakers within the double-branch arrangement, could transfer to the other circuit breaker, resulting in a phase-to-phase electrical fault. The ionized gases could also cause a phase-to-ground failure with any metallic enclosure within which the circuit breaker is mounted. This can lead to electrical faults on the line side of the circuit breakers and damage to switchgear equipment.
To prevent electrical faults caused by conductive ionized gases, known prior art panelboard assemblies employ gas barriers.
Fiberboard barriers are often used to prevent ionized exhaust gases discharged from one circuit breaker from entering the line lug compartments of the opposing circuit breaker. However, over long periods of continuous use, the fiber material can become brittle and deteriorate. Additionally, because such fiberboard barriers are removable for access to the line terminals, subsequent connection of the circuit breakers to line terminal straps without replacing the barrier is possible, thus creating a path for ionized gases to potentially cause a phase-to-phase and/or phase-to-ground electrical fault.
U.S. Pat. No. 4,965,544 discloses a molded case circuit breaker exhaust barrier for direct attachment to the circuit breaker terminal straps in the absence of line terminal lugs. The barrier includes hinged extension baffles for insertion within the line strap compartments of adjacent circuit breakers connected within a panelboard in a double-branch arrangement. The extensions are inserted within openings formed in the case of the circuit breaker to electrically insulate the line strap connectors from ionized exhaust gases. Although the disclosed barrier insulates the line strap connectors, discharged ionized gases are not segregated or controllably directed.
U.S. Pat. No. 5,150,091 discloses lug and bus covers for molded case circuit breakers to electrically insulate line and load straps. An integrally formed baffle and press-fit retention arrangement requires no separate fastening mechanism for attachment to the ends of an industrial-rated circuit breaker. A bus cover attaches to the line ends of opposing circuit breakers connected within a panelboard in double-branch configuration to prevent exhaust gases from one circuit breaker, experiencing a severe overcurrent fault condition in one phase of a multi-phase power system, from reaching the other phase connections within the opposing circuit breaker. However, the disclosed lug and bus covers are separate units requiring attachment to each end of each circuit breaker within the panelboard assembly.
There is a need, therefore, for a simplified, single gas segregator barrier integral with the panelboard assembly and capable of quenching and controllably directing discharged ionized gases.
Accordingly, there is room for improvement in gas segregator barriers for electrical switching apparatus and in panelboard assemblies employing ionized gas segregator barriers.